Porosity evolution study in irradiated UO2 fuel based on fuel matrix swelling

Abstract The volume porosity of irradiated UO2 fuel in the form of a correlation is developed which includes two individual parts as the pore and swelling porosity in terms of the local density and fractional matrix swelling. Based on a low temperature swelling model for UO2 fuel, the matrix swelling terms are calculated and the evolution of porosity up to burn-up levels of 120 MWd/KgU is presented. It is seen that for high burn-up PWR fuel pellet rim, the dominant contribution to total porosity comes from pores generated due to Xe depletion in the ceramic matrix while the nearly constant swelling porosity makes a small contribution to the total porosity. The porosity evolution is also validated by comparing against experimental data and a fairly good agreement was found.